Wicked Cool Antennas

I'm from San Francisco, but I've lived more than half my life in New England, and have gradually learned the language. The adjective "wicked" is frequently applied in these parts to mean "exceptional", or "cool", so "wicked cool", a term frequently heard, must imply something really special. For our purposes here today, it does indeed.

Last week I had a briefing with a small company I'd heard of, but really didn't know all that much about, Fidelity Comtech. They do a fair amount of work on government systems, but have now developed a commercial line of Wi-Fi APs based on a powerful and complex antenna technology called phased arrays. You can think of a phased array as a multi-element, steerable electronic antenna. Of course, steerable antennas have been around for a long time; you've seen rotating radar antennas, for example, at airports and in those great cold-war movies from the ‘50s. But phased arrays steer without physically moving. The best example is seen in the massive PAVE PAWS over-the-horizon early-warning radar, deployed in a few locations around the country, including not far from me on Cape Cod. The ability of phased arrays to focus energy in a particular direction, and even track moving objects, can dramatically improve the quality of the link, with all of the associated benefits therein.

The problem with most phased arrays is that, like PAVE PAWS, they are planar and thus mostly directional, albeit with some steerablity. Most wireless infrastructure applications, like WLANs, however, need omnidirectional (360-degree) coverage, because they don't know where the other end of the connection might be at any given moment. So while a phased array is always useful in focusing energy on moving clients, and also of benefit on the receive end, low-gain omnidirectional dipoles are almost always used in WLANs. You'll occasionally see, however, phased arrays used in cellular apps, although three separate arrays are required to address the full circle of coverage. But the cellular guys have lots of money and can amortize their investment over a very wide area indeed.

So what Fidelity Comtech has done is to develop a phased array that can in fact cover 360 degrees, focusing energy where it's needed at any particular moment. Their antenna is part of an AP designed for outdoor mounting, and optimized for (as you might guess) coverage - they claim 4X typical. While the product is more expensive (US$11,000) than typical outdoor APs, a solution using this product can be cheaper than the usual alternative because less infrastructure is required and the labor-intensive design and installation costs will be correspondingly lower. So look for these in transportation, logistics, storage yards, and other similar large, outdoor venues.

But the implications of the omnidirectional phased array go much further. This antenna is particularly good in location and tracking applications and in dealing with interference. And imagine a similar design, miniaturized to fit in a WLAN client device, or even a handset. OK, that may be a ways out, but keep your eye on this one - as I've long said, the antenna is the most important part of the radio. And phased arrays are perhaps the most important direction for antennas.